How do I set up a serial console on Debian Linux HP server for troubleshooting and login purpose?
To setup a serial console you need to edit the following files under Debian Linux:
- /boot/grub/menu.lst or /etc/default/grub (recommended for grub2)
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4 /dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3 /dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4 /dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
/dev/ttyS0 (COM1) is detected and working serial console under Linux. For testing purpose, I’m going to set baud rate to 19200 and terminal type to vt100.
Grub Configuration (Grub2)
Edit /etc/default/grub, enter:
# vi /etc/default/grub
Append / modify as follows:
GRUB_CMDLINE_LINUX='console=tty0 console=ttyS0,19200n8' GRUB_TERMINAL=serial GRUB_SERIAL_COMMAND="serial --speed=19200 --unit=0 --word=8 --parity=no --stop=1"
Save and close the file. Next run the following command to generate a grub2 config file /boot/grub/grub.cfg :
A Note About Grub Legacy (older version)
If you are not using GRUB2 update /boot/grub/menu.lst (grub legacy) with kernel line as follows with console port, and baud rate:
title Debian GNU/Linux, kernel 2.6.32-5-486 root (hd0,0) kernel /boot/vmlinuz-2.6.32-5-486 root=UUID=b598f856-2a2a-46d5-b60a-95826cfc7bf6 ro console=ttyS0,19200 earlyprint=serial,ttyS0,19200 initrd /boot/initrd.img-2.6.32-5-486
Save and close the file.
Edit /etc/inittab, enter:
# vi /etc/inittab
You need put a getty on a serial line for a terminal:
T0:23:respawn:/sbin/getty -L ttyS0 19200 vt100
Save and close the file.
Edit /etc/securetty, enter:
# vi /etc/securetty
Make sure UART serial ports /dev/ttyS0 is listed:
Save and close the file. Now, you can reboot the server for testing purpose.
How Do I Connect Using a Serial Console?
You need to use the minicom command, which is a communication program that runs under most unices. You can install minicom as follows on your Debian / Ubuntu desktop system:
# apt-get install minicom
For rpm based distro such as RHEL / Fedora / CentOS Linux, enter:
# yum install minicom
Run minicom as follows to create a configuration file:
# minicom -s -c on
Press [down] key and select Serial port setup:
- Press A to setup serial device name such as /dev/ttyS0
- Press E to setup Bps/Par/Bits (baud rate)
- Press [ESC] to exit
- From menu select “Save setup as DFL”
Alternatively, you can create minicom config DFL file as follows:
# cat /etc/minicom/minirc.dfl
pu port /dev/ttyS0
pu baudrate 19200
pu bits 8
pu parity N
pu stopbits 1
pu rtscts No
Save and close the file. To connect to a serial console simply type the minicom command as follows:
How Do I Connect From MS-Windows XP / 2000 / Vista / 7 Desktop System?
You can use the HyperTerminal or putty client as described here.
How Do I Connect To a Serial Console Over IP Network?
You need to use the KVM over IP client as described here or use the ipmitool command line tool for serial console redirection over IP (LAN/WAN). It is highly recommend that you access server over a serial console using some sort of VPN to encrypt all traffic.